Rendering stack of 2D images as a 3D object?
You can definitely render a 3D voxel dataset using the built-in tools of Blender. As seen in the example below:

The basic workflow using the Blender Internal engine:


Create a Cube that's the same dimension as your voxel data ( image resolution x Voxal size , the important thing is to preserve the dimension ratios )
Create a volume material and texture for the cube.
Load in the density data as image sequence or 8bit raw data ( tested .img and .rawb formats ).
Adjust all resolution parameters ( set it to the resolution of the image you should have this information , incorrect resolution will result in distorted/cropped or even no visible result )
setup the texture to affect Density and Emissions.
Tweak color map and material properties until the data is shown nicely.


The material and texture setup :



the render result :



Using the color ramp, you can even remap the density to different colors.